drivers/iio/humidity/am2315.c

   1 /**
   2  * Aosong AM2315 relative humidity and temperature
   3  *
   4  * Copyright (c) 2016, Intel Corporation.
   5  *
   6  * This file is subject to the terms and conditions of version 2 of
   7  * the GNU General Public License. See the file COPYING in the main
   8  * directory of this archive for more details.
   9  *
  10  * 7-bit I2C address: 0x5C.
  11  */
  12
  13 #include <linux/acpi.h>
  14 #include <linux/delay.h>
  15 #include <linux/i2c.h>
  16 #include <linux/kernel.h>
  17 #include <linux/module.h>
  18 #include <linux/iio/buffer.h>
  19 #include <linux/iio/iio.h>
  20 #include <linux/iio/sysfs.h>
  21 #include <linux/iio/trigger_consumer.h>
  22 #include <linux/iio/triggered_buffer.h>
  23
  24 #define AM2315_REG_HUM_MSB                      0x00
  25 #define AM2315_REG_HUM_LSB                      0x01
  26 #define AM2315_REG_TEMP_MSB                     0x02
  27 #define AM2315_REG_TEMP_LSB                     0x03
  28
  29 #define AM2315_FUNCTION_READ                    0x03
  30 #define AM2315_HUM_OFFSET                       2
  31 #define AM2315_TEMP_OFFSET                      4
  32 #define AM2315_ALL_CHANNEL_MASK                 GENMASK(1, 0)
  33
  34 #define AM2315_DRIVER_NAME                      "am2315"
  35
  36 struct am2315_data {
  37         struct i2c_client *client;
  38         struct mutex lock;
  39         s16 buffer[8]; /* 2x16-bit channels + 2x16 padding + 4x16 timestamp */
  40 };
  41
  42 struct am2315_sensor_data {
  43         s16 hum_data;
  44         s16 temp_data;
  45 };
  46
  47 static const struct iio_chan_spec am2315_channels[] = {
  48         {
  49                 .type = IIO_HUMIDITYRELATIVE,
  50                 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
  51                                       BIT(IIO_CHAN_INFO_SCALE),
  52                 .scan_index = 0,
  53                 .scan_type = {
  54                         .sign = 's',
  55                         .realbits = 16,
  56                         .storagebits = 16,
  57                         .endianness = IIO_CPU,
  58                 },
  59         },
  60         {
  61                 .type = IIO_TEMP,
  62                 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
  63                                       BIT(IIO_CHAN_INFO_SCALE),
  64                 .scan_index = 1,
  65                 .scan_type = {
  66                         .sign = 's',
  67                         .realbits = 16,
  68                         .storagebits = 16,
  69                         .endianness = IIO_CPU,
  70                 },
  71         },
  72         IIO_CHAN_SOFT_TIMESTAMP(2),
  73 };
  74
  75 /* CRC calculation algorithm, as specified in the datasheet (page 13). */
  76 static u16 am2315_crc(u8 *data, u8 nr_bytes)
  77 {
  78         int i;
  79         u16 crc = 0xffff;
  80
  81         while (nr_bytes--) {
  82                 crc ^= *data++;
  83                 for (i = 0; i < 8; i++) {
  84                         if (crc & 0x01) {
  85                                 crc >>= 1;
  86                                 crc ^= 0xA001;
  87                         } else {
  88                                 crc >>= 1;
  89                         }
  90                 }
  91         }
  92
  93         return crc;
  94 }
  95
  96 /* Simple function that sends a few bytes to the device to wake it up. */
  97 static void am2315_ping(struct i2c_client *client)
  98 {
  99         i2c_smbus_read_byte_data(client, AM2315_REG_HUM_MSB);
 100 }
 101
 102 static int am2315_read_data(struct am2315_data *data,
 103                             struct am2315_sensor_data *sensor_data)
 104 {
 105         int ret;
 106         /* tx_buf format: <function code> <start addr> <nr of regs to read> */
 107         u8 tx_buf[3] = { AM2315_FUNCTION_READ, AM2315_REG_HUM_MSB, 4 };
 108         /*
 109          * rx_buf format:
 110          * <function code> <number of registers read>
 111          * <humidity MSB> <humidity LSB> <temp MSB> <temp LSB>
 112          * <CRC LSB> <CRC MSB>
 113          */
 114         u8 rx_buf[8];
 115         u16 crc;
 116
 117         /* First wake up the device. */
 118         am2315_ping(data->client);
 119
 120         mutex_lock(&data->lock);
 121         ret = i2c_master_send(data->client, tx_buf, sizeof(tx_buf));
 122         if (ret < 0) {
 123                 dev_err(&data->client->dev, "failed to send read request\n");
 124                 goto exit_unlock;
 125         }
 126         /* Wait 2-3 ms, then read back the data sent by the device. */
 127         usleep_range(2000, 3000);
 128         /* Do a bulk data read, then pick out what we need. */
 129         ret = i2c_master_recv(data->client, rx_buf, sizeof(rx_buf));
 130         if (ret < 0) {
 131                 dev_err(&data->client->dev, "failed to read sensor data\n");
 132                 goto exit_unlock;
 133         }
 134         mutex_unlock(&data->lock);
 135         /*
 136          * Do a CRC check on the data and compare it to the value
 137          * calculated by the device.
 138          */
 139         crc = am2315_crc(rx_buf, sizeof(rx_buf) - 2);
 140         if ((crc & 0xff) != rx_buf[6] || (crc >> 8) != rx_buf[7]) {
 141                 dev_err(&data->client->dev, "failed to verify sensor data\n");
 142                 return -EIO;
 143         }
 144
 145         sensor_data->hum_data = (rx_buf[AM2315_HUM_OFFSET] << 8) |
 146                                  rx_buf[AM2315_HUM_OFFSET + 1];
 147         sensor_data->temp_data = (rx_buf[AM2315_TEMP_OFFSET] << 8) |
 148                                   rx_buf[AM2315_TEMP_OFFSET + 1];
 149
 150         return ret;
 151
 152 exit_unlock:
 153         mutex_unlock(&data->lock);
 154         return ret;
 155 }
 156
 157 static irqreturn_t am2315_trigger_handler(int irq, void *p)
 158 {
 159         int i;
 160         int ret;
 161         int bit;
 162         struct iio_poll_func *pf = p;
 163         struct iio_dev *indio_dev = pf->indio_dev;
 164         struct am2315_data *data = iio_priv(indio_dev);
 165         struct am2315_sensor_data sensor_data;
 166
 167         ret = am2315_read_data(data, &sensor_data);
 168         if (ret < 0)
 169                 goto err;
 170
 171         mutex_lock(&data->lock);
 172         if (*(indio_dev->active_scan_mask) == AM2315_ALL_CHANNEL_MASK) {
 173                 data->buffer[0] = sensor_data.hum_data;
 174                 data->buffer[1] = sensor_data.temp_data;
 175         } else {
 176                 i = 0;
 177                 for_each_set_bit(bit, indio_dev->active_scan_mask,
 178                                  indio_dev->masklength) {
 179                         data->buffer[i] = (bit ? sensor_data.temp_data :
 180                                                  sensor_data.hum_data);
 181                         i++;
 182                 }
 183         }
 184         mutex_unlock(&data->lock);
 185
 186         iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
 187                                            pf->timestamp);
 188 err:
 189         iio_trigger_notify_done(indio_dev->trig);
 190         return IRQ_HANDLED;
 191 }
 192
 193 static int am2315_read_raw(struct iio_dev *indio_dev,
 194                            struct iio_chan_spec const *chan,
 195                            int *val, int *val2, long mask)
 196 {
 197         int ret;
 198         struct am2315_sensor_data sensor_data;
 199         struct am2315_data *data = iio_priv(indio_dev);
 200
 201         switch (mask) {
 202         case IIO_CHAN_INFO_RAW:
 203                 ret = am2315_read_data(data, &sensor_data);
 204                 if (ret < 0)
 205                         return ret;
 206                 *val = (chan->type == IIO_HUMIDITYRELATIVE) ?
 207                                 sensor_data.hum_data : sensor_data.temp_data;
 208                 return IIO_VAL_INT;
 209         case IIO_CHAN_INFO_SCALE:
 210                 *val = 100;
 211                 return IIO_VAL_INT;
 212         }
 213
 214         return -EINVAL;
 215 }
 216
 217 static const struct iio_info am2315_info = {
 218         .driver_module          = THIS_MODULE,
 219         .read_raw               = am2315_read_raw,
 220 };
 221
 222 static int am2315_probe(struct i2c_client *client,
 223                         const struct i2c_device_id *id)
 224 {
 225         int ret;
 226         struct iio_dev *indio_dev;
 227         struct am2315_data *data;
 228
 229         indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
 230         if (!indio_dev) {
 231                 dev_err(&client->dev, "iio allocation failed!\n");
 232                 return -ENOMEM;
 233         }
 234
 235         data = iio_priv(indio_dev);
 236         data->client = client;
 237         i2c_set_clientdata(client, indio_dev);
 238         mutex_init(&data->lock);
 239
 240         indio_dev->dev.parent = &client->dev;
 241         indio_dev->info = &am2315_info;
 242         indio_dev->name = AM2315_DRIVER_NAME;
 243         indio_dev->modes = INDIO_DIRECT_MODE;
 244         indio_dev->channels = am2315_channels;
 245         indio_dev->num_channels = ARRAY_SIZE(am2315_channels);
 246
 247         ret = iio_triggered_buffer_setup(indio_dev, NULL,
 248                                          am2315_trigger_handler, NULL);
 249         if (ret < 0) {
 250                 dev_err(&client->dev, "iio triggered buffer setup failed\n");
 251                 return ret;
 252         }
 253
 254         ret = iio_device_register(indio_dev);
 255         if (ret < 0)
 256                 goto err_buffer_cleanup;
 257
 258         return 0;
 259
 260 err_buffer_cleanup:
 261         iio_triggered_buffer_cleanup(indio_dev);
 262         return ret;
 263 }
 264
 265 static int am2315_remove(struct i2c_client *client)
 266 {
 267         struct iio_dev *indio_dev = i2c_get_clientdata(client);
 268
 269         iio_device_unregister(indio_dev);
 270         iio_triggered_buffer_cleanup(indio_dev);
 271
 272         return 0;
 273 }
 274
 275 static const struct i2c_device_id am2315_i2c_id[] = {
 276         {"am2315", 0},
 277         {}
 278 };
 279 MODULE_DEVICE_TABLE(i2c, am2315_i2c_id);
 280
 281 static const struct acpi_device_id am2315_acpi_id[] = {
 282         {"AOS2315", 0},
 283         {}
 284 };
 285
 286 MODULE_DEVICE_TABLE(acpi, am2315_acpi_id);
 287
 288 static struct i2c_driver am2315_driver = {
 289         .driver = {
 290                 .name = "am2315",
 291                 .acpi_match_table = ACPI_PTR(am2315_acpi_id),
 292         },
 293         .probe =            am2315_probe,
 294         .remove =           am2315_remove,
 295         .id_table =         am2315_i2c_id,
 296 };
 297
 298 module_i2c_driver(am2315_driver);
 299
 300 MODULE_AUTHOR("Tiberiu Breana <tiberiu.a.breana@intel.com>");
 301 MODULE_DESCRIPTION("Aosong AM2315 relative humidity and temperature");
 302 MODULE_LICENSE("GPL v2");